Unit 5 | MNGT 801 Notes | Solar Energy Technology and Applications Notes | AKTU Notes

5.1 What are Integrated Energy Systems?

An integrated energy system combines two or more energy sources and/or conversion technologies working together to meet energy needs more efficiently and reliably.

Why integrate?

• No single energy source is perfect.
• Solar is available only during daytime.
• Wind is seasonal.
• Fossil fuels pollute.
• By combining them, we get a system that is more reliable, efficient, and clean.

5.2 Conventional vs Non-Conventional Energy Sources

Conventional (Traditional) Energy Sources:

• Fossil fuels: Coal, oil, natural gas
• Large hydro: Big dams
• Nuclear: Uranium fission

These are well-established and can produce large amounts of power. But they cause pollution, are limited, and are expensive in the long run.

Non-Conventional (Renewable) Energy Sources:

• Solar: PV and thermal
• Wind: Wind turbines
• Small hydro: Mini/micro hydro plants
• Biomass: Agricultural waste, cow dung
• Geothermal: Earth's heat
• Tidal: Ocean tides

These are clean, renewable, and freely available. But they are intermittent (not available 24/7) and need storage or backup.

5.3 Concept of Integration

Integration means making different energy systems work together as a team.

Example 1 – Solar + Wind:

• Solar produces power during daytime, wind produces power day and night.
• Together, they provide more consistent power than either alone.

Example 2 – Solar + Diesel Generator:

• Solar PV provides power during day.
• Diesel generator takes over at night or on cloudy days.
• This is called a Solar-Diesel Hybrid System.
• Reduces diesel consumption by 50–80%.

Example 3 – Solar + Battery Storage:

• Solar power is stored in batteries during the day.
• Batteries supply power at night.
• Fully off-grid, zero pollution, used in homes and telecom towers.

Example 4 – Solar + Biomass:

• Solar provides heat/electricity during day.
• Biomass gasifier/biogas provides energy at night.
• Suitable for rural communities.

Example 5 – Solar + Grid (Grid-Tied System):

• Solar panels supply power to home during day.
• Excess power is exported to the grid (you earn money).
• Grid supplies power at night or on rainy days.
• This is called net metering — the electricity meter runs backwards when you export.

5.4 Types of Integrated Energy Systems

1. Hybrid Power Systems:

• Combine two or more generation sources.
• Example: Solar-Wind-Diesel hybrid for remote villages.

2. Cogeneration (Combined Heat and Power – CHP):

• A single system produces both electricity and useful heat simultaneously.
• Example: Solar thermal power plant that also supplies process heat to industries.
• Efficiency of CHP: up to 80–90% vs 35–40% for separate systems.

3. Tri-generation:

• Produces electricity + heat + cooling simultaneously.
• Also called CCHP (Combined Cooling, Heating, and Power).

4. Microgrids:

• A small, local power grid that includes solar, storage, and other sources.
• Can work connected to the main grid or independently (islanded mode).
• Very useful for hospitals, campuses, villages.

5.5 Integrated Energy System Design

Designing an integrated system requires careful planning.

Steps in Design:

Step 1 – Load Analysis:

• Calculate the total energy demand (electrical + thermal).
• Know the hourly/daily/seasonal variation of load.

Step 2 – Resource Assessment:

• Find out available solar, wind, biomass resources at the location.
• Check solar radiation data, wind speed data.

Step 3 – Component Sizing:

• Decide the capacity of solar panels, wind turbine, battery, generator, etc.
• Should meet load with minimum cost and maximum reliability.

Step 4 – System Configuration:

• Decide how components will be connected (series, parallel, AC bus, DC bus).

Step 5 – Control Strategy:

• Decide which source runs when.
• Usually: Solar first → then battery → then grid/diesel as backup.

Software Tools Used:

• HOMER (Hybrid Optimization Model for Electric Renewables) — most popular.
• RETScreen
• MATLAB/Simulink

5.6 Economics of Integrated Energy Systems

Even if a renewable system is costly to install, it may be cheaper in the long run.

Key Economic Terms:

1. Capital Cost (Initial Investment):

• Cost of buying and installing solar panels, wind turbines, batteries, inverters, etc.
• Solar systems: ₹40,000–₹60,000 per kW installed.

2. Operating and Maintenance (O&M) Cost:

• Ongoing cost: cleaning panels, replacing batteries every 5–10 years, minor repairs.
• Solar has very low O&M cost — no moving parts.

3. Life of System:

• Solar panels: 25–30 years
• Batteries: 5–10 years
• Wind turbine: 20–25 years

4. Levelized Cost of Energy (LCOE):

• Total cost over system's life ÷ Total energy generated over lifetime
• LCOE of solar in India: ₹2–3 per kWh (very competitive with coal: ₹3–5/kWh)

5. Payback Period:

• Time taken to recover the initial investment through savings.
• Typical solar system payback: 4–7 years (then free electricity for 20+ years!)

6. Net Present Value (NPV) and Internal Rate of Return (IRR):

• Used to decide if the investment is financially worth it.
• Positive NPV = Good investment.

Benefits of Integration:

• Reduced fuel costs
• Energy security — not dependent on one source
• Environmental benefits — reduced CO₂ emissions
• Job creation in rural areas